initsplan.c

/*------------------------------------------------------------------------- * * initsplan.c * Target list, qualification, joininfo initialization routines * * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * * * IDENTIFICATION * $PostgreSQL: pgsql/src/backend/optimizer/plan/initsplan.c,v 1.154.2.1 2009/07/21 02:02:51 tgl Exp $ * *------------------------------------------------------------------------- */#include "postgres.h"#include "catalog/pg_operator.h"#include "catalog/pg_type.h"#include "optimizer/clauses.h"#include "optimizer/cost.h"#include "optimizer/joininfo.h"#include "optimizer/pathnode.h"#include "optimizer/paths.h"#include "optimizer/placeholder.h"#include "optimizer/planmain.h"#include "optimizer/prep.h"#include "optimizer/restrictinfo.h"#include "optimizer/var.h"#include "parser/parse_expr.h"#include "parser/parse_oper.h"#include "utils/builtins.h"#include "utils/lsyscache.h"#include "utils/syscache.h"/* These parameters are set by GUC */int from_collapse_limit;
int join_collapse_limit;
staticList *deconstruct_recurse(PlannerInfo *root, Node *jtnode,
bool below_outer_join,
Relids *qualscope, Relids *inner_join_rels);
staticSpecialJoinInfo *make_outerjoininfo(PlannerInfo *root,
Relids left_rels, Relids right_rels,
Relids inner_join_rels,
JoinType jointype, List *clause);
staticvoid distribute_qual_to_rels(PlannerInfo *root, Node *clause,
bool is_deduced,
bool below_outer_join,
JoinType jointype,
Relids qualscope,
Relids ojscope,
Relids outerjoin_nonnullable);
staticbool check_outerjoin_delay(PlannerInfo *root, Relids *relids_p,
Relids *nullable_relids_p, bool is_pushed_down);
staticbool check_redundant_nullability_qual(PlannerInfo *root, Node *clause);
staticvoid check_mergejoinable(RestrictInfo *restrictinfo);
staticvoid check_hashjoinable(RestrictInfo *restrictinfo);
/***************************************************************************** * * JOIN TREES * *****************************************************************************//* * add_base_rels_to_query * * Scan the query's jointree and create baserel RelOptInfos for all * the base relations (ie, table, subquery, and function RTEs) * appearing in the jointree. * * The initial invocation must pass root->parse->jointree as the value of * jtnode. Internally, the function recurses through the jointree. * * At the end of this process, there should be one baserel RelOptInfo for * every non-join RTE that is used in the query. Therefore, this routine * is the only place that should call build_simple_rel with reloptkind * RELOPT_BASEREL. (Note: build_simple_rel recurses internally to build * "other rel" RelOptInfos for the members of any appendrels we find here.) */void
add_base_rels_to_query(PlannerInfo *root, Node *jtnode)
{
if (jtnode == NULL)
return;
if (IsA(jtnode, RangeTblRef))
{
int varno = ((RangeTblRef *) jtnode)->rtindex;
(void) build_simple_rel(root, varno, RELOPT_BASEREL);
}
elseif (IsA(jtnode, FromExpr))
{
FromExpr *f = (FromExpr *) jtnode;
ListCell *l;
foreach(l, f->fromlist)
add_base_rels_to_query(root, lfirst(l));
}
elseif (IsA(jtnode, JoinExpr))
{
JoinExpr *j = (JoinExpr *) jtnode;
add_base_rels_to_query(root, j->larg);
add_base_rels_to_query(root, j->rarg);
}
else
elog(ERROR, "unrecognized node type: %d",
(int) nodeTag(jtnode));
}
/***************************************************************************** * * TARGET LISTS * *****************************************************************************//* * build_base_rel_tlists * Add targetlist entries for each var needed in the query's final tlist * to the appropriate base relations. * * We mark such vars as needed by "relation 0" to ensure that they will * propagate up through all join plan steps. */void
build_base_rel_tlists(PlannerInfo *root, List *final_tlist)
{
List *tlist_vars = pull_var_clause((Node *) final_tlist,
PVC_INCLUDE_PLACEHOLDERS);
if (tlist_vars != NIL)
{
add_vars_to_targetlist(root, tlist_vars, bms_make_singleton(0));
list_free(tlist_vars);
}
}
/* * add_vars_to_targetlist * For each variable appearing in the list, add it to the owning * relation's targetlist if not already present, and mark the variable * as being needed for the indicated join (or for final output if * where_needed includes "relation 0"). * * The list may also contain PlaceHolderVars. These don't necessarily * have a single owning relation; we keep their attr_needed info in * root->placeholder_list instead. */void
add_vars_to_targetlist(PlannerInfo *root, List *vars, Relids where_needed)
{
ListCell *temp;
Assert(!bms_is_empty(where_needed));
foreach(temp, vars)
{
Node *node = (Node *) lfirst(temp);
if (IsA(node, Var))
{
Var *var = (Var *) node;
RelOptInfo *rel = find_base_rel(root, var->varno);
int attno = var->varattno;
Assert(attno >= rel->min_attr && attno <= rel->max_attr);
attno -= rel->min_attr;
if (rel->attr_needed[attno] == NULL)
{
/* Variable not yet requested, so add to reltargetlist *//* XXX is copyObject necessary here? */
rel->reltargetlist = lappend(rel->reltargetlist,
copyObject(var));
}
rel->attr_needed[attno] = bms_add_members(rel->attr_needed[attno],
where_needed);
}
elseif (IsA(node, PlaceHolderVar))
{
PlaceHolderVar *phv = (PlaceHolderVar *) node;
PlaceHolderInfo *phinfo = find_placeholder_info(root, phv);
phinfo->ph_needed = bms_add_members(phinfo->ph_needed,
where_needed);
}
else
elog(ERROR, "unrecognized node type: %d", (int) nodeTag(node));
}
}
/***************************************************************************** * * JOIN TREE PROCESSING * *****************************************************************************//* * deconstruct_jointree * Recursively scan the query's join tree for WHERE and JOIN/ON qual * clauses, and add these to the appropriate restrictinfo and joininfo * lists belonging to base RelOptInfos. Also, add SpecialJoinInfo nodes * to root->join_info_list for any outer joins appearing in the query tree. * Return a "joinlist" data structure showing the join order decisions * that need to be made by make_one_rel(). * * The "joinlist" result is a list of items that are either RangeTblRef * jointree nodes or sub-joinlists. All the items at the same level of * joinlist must be joined in an order to be determined by make_one_rel() * (note that legal orders may be constrained by SpecialJoinInfo nodes). * A sub-joinlist represents a subproblem to be planned separately. Currently * sub-joinlists arise only from FULL OUTER JOIN or when collapsing of * subproblems is stopped by join_collapse_limit or from_collapse_limit. * * NOTE: when dealing with inner joins, it is appropriate to let a qual clause * be evaluated at the lowest level where all the variables it mentions are * available. However, we cannot push a qual down into the nullable side(s) * of an outer join since the qual might eliminate matching rows and cause a * NULL row to be incorrectly emitted by the join. Therefore, we artificially * OR the minimum-relids of such an outer join into the required_relids of * clauses appearing above it. This forces those clauses to be delayed until * application of the outer join (or maybe even higher in the join tree). */List *
deconstruct_jointree(PlannerInfo *root)
{
Relids qualscope;
Relids inner_join_rels;
/* Start recursion at top of jointree */
Assert(root->parse->jointree != NULL &&
IsA(root->parse->jointree, FromExpr));
return deconstruct_recurse(root, (Node *) root->parse->jointree, false,
&qualscope, &inner_join_rels);
}
/* * deconstruct_recurse * One recursion level of deconstruct_jointree processing. * * Inputs: * jtnode is the jointree node to examine * below_outer_join is TRUE if this node is within the nullable side of a * higher-level outer join * Outputs: * *qualscope gets the set of base Relids syntactically included in this * jointree node (do not modify or free this, as it may also be pointed * to by RestrictInfo and SpecialJoinInfo nodes) * *inner_join_rels gets the set of base Relids syntactically included in * inner joins appearing at or below this jointree node (do not modify * or free this, either) * Return value is the appropriate joinlist for this jointree node * * In addition, entries will be added to root->join_info_list for outer joins. */staticList *
deconstruct_recurse(PlannerInfo *root, Node *jtnode, bool below_outer_join,
Relids *qualscope, Relids *inner_join_rels)
{
List *joinlist;
if (jtnode == NULL)
{
*qualscope = NULL;
*inner_join_rels = NULL;
return NIL;
}
if (IsA(jtnode, RangeTblRef))
{
int varno = ((RangeTblRef *) jtnode)->rtindex;
/* No quals to deal with, just return correct result */
*qualscope = bms_make_singleton(varno);
/* A single baserel does not create an inner join */
*inner_join_rels = NULL;
joinlist = list_make1(jtnode);
}
elseif (IsA(jtnode, FromExpr))
{
FromExpr *f = (FromExpr *) jtnode;
int remaining;
ListCell *l;
/* * First, recurse to handle child joins. We collapse subproblems into * a single joinlist whenever the resulting joinlist wouldn't exceed * from_collapse_limit members. Also, always collapse one-element * subproblems, since that won't lengthen the joinlist anyway. */
*qualscope = NULL;
*inner_join_rels = NULL;
joinlist = NIL;
remaining = list_length(f->fromlist);
foreach(l, f->fromlist)
{
Relids sub_qualscope;
List *sub_joinlist;
int sub_members;
sub_joinlist = deconstruct_recurse(root, lfirst(l),
below_outer_join,
&sub_qualscope,
inner_join_rels);
*qualscope = bms_add_members(*qualscope, sub_qualscope);
sub_members = list_length(sub_joinlist);
remaining--;
if (sub_members <= 1 ||
list_length(joinlist) + sub_members + remaining <= from_collapse_limit)
joinlist = list_concat(joinlist, sub_joinlist);
else
joinlist = lappend(joinlist, sub_joinlist);
}
/* * A FROM with more than one list element is an inner join subsuming * all below it, so we should report inner_join_rels = qualscope. If * there was exactly one element, we should (and already did) report * whatever its inner_join_rels were. If there were no elements (is * that possible?) the initialization before the loop fixed it. */if (list_length(f->fromlist) > 1)
*inner_join_rels = *qualscope;
/* * Now process the top-level quals. */foreach(l, (List *) f->quals)
{
Node *qual = (Node *) lfirst(l);
distribute_qual_to_rels(root, qual,
false, below_outer_join, JOIN_INNER,
*qualscope, NULL, NULL);
}
}
elseif (IsA(jtnode, JoinExpr))
{
JoinExpr *j = (JoinExpr *) jtnode;
Relids leftids,
rightids,
left_inners,
right_inners,
nonnullable_rels,
ojscope;
List *leftjoinlist,
*rightjoinlist;
SpecialJoinInfo *sjinfo;
ListCell *l;
/* * Order of operations here is subtle and critical. First we recurse * to handle sub-JOINs. Their join quals will be placed without * regard for whether this level is an outer join, which is correct. * Then we place our own join quals, which are restricted by lower * outer joins in any case, and are forced to this level if this is an * outer join and they mention the outer side. Finally, if this is an * outer join, we create a join_info_list entry for the join. This * will prevent quals above us in the join tree that use those rels * from being pushed down below this level. (It's okay for upper * quals to be pushed down to the outer side, however.) */switch (j->jointype)
{
case JOIN_INNER:
leftjoinlist = deconstruct_recurse(root, j->larg,
below_outer_join,
&leftids, &left_inners);
rightjoinlist = deconstruct_recurse(root, j->rarg,
below_outer_join,
&rightids, &right_inners);
*qualscope = bms_union(leftids, rightids);
*inner_join_rels = *qualscope;
/* Inner join adds no restrictions for quals */
nonnullable_rels = NULL;
break;
case JOIN_LEFT:
case JOIN_ANTI:
leftjoinlist = deconstruct_recurse(root, j->larg,
below_outer_join,
&leftids, &left_inners);
rightjoinlist = deconstruct_recurse(root, j->rarg,
true,
&rightids, &right_inners);
*qualscope = bms_union(leftids, rightids);
*inner_join_rels = bms_union(left_inners, right_inners);
nonnullable_rels = leftids;
break;
case JOIN_SEMI:
leftjoinlist = deconstruct_recurse(root, j->larg,
below_outer_join,
&leftids, &left_inners);
rightjoinlist = deconstruct_recurse(root, j->rarg,
below_outer_join,
&rightids, &right_inners);
*qualscope = bms_union(leftids, rightids);
*inner_join_rels = bms_union(left_inners, right_inners);
/* Semi join adds no restrictions for quals */
nonnullable_rels = NULL;
break;
case JOIN_FULL:
leftjoinlist = deconstruct_recurse(root, j->larg,
true,
&leftids, &left_inners);
rightjoinlist = deconstruct_recurse(root, j->rarg,
true,
&rightids, &right_inners);
*qualscope = bms_union(leftids, rightids);
*inner_join_rels = bms_union(left_inners, right_inners);
/* each side is both outer and inner */
nonnullable_rels = *qualscope;
break;
default:
/* JOIN_RIGHT was eliminated during reduce_outer_joins() */
elog(ERROR, "unrecognized join type: %d",
(int) j->jointype);
nonnullable_rels = NULL; /* keep compiler quiet */
leftjoinlist = rightjoinlist = NIL;
break;
}
/* * For an OJ, form the SpecialJoinInfo now, because we need the OJ's * semantic scope (ojscope) to pass to distribute_qual_to_rels. But * we mustn't add it to join_info_list just yet, because we don't want * distribute_qual_to_rels to think it is an outer join below us. * * Semijoins are a bit of a hybrid: we build a SpecialJoinInfo, but we * want ojscope = NULL for distribute_qual_to_rels. */if (j->jointype != JOIN_INNER)
{
sjinfo = make_outerjoininfo(root,
leftids, rightids,
*inner_join_rels,
j->jointype,
(List *) j->quals);
if (j->jointype == JOIN_SEMI)
ojscope = NULL;
else
ojscope = bms_union(sjinfo->min_lefthand,
sjinfo->min_righthand);
}
else
{
sjinfo = NULL;
ojscope = NULL;
}
/* Process the qual clauses */foreach(l, (List *) j->quals)
{
Node *qual = (Node *) lfirst(l);
distribute_qual_to_rels(root, qual,
false, below_outer_join, j->jointype,
*qualscope,
ojscope, nonnullable_rels);
}
/* Now we can add the SpecialJoinInfo to join_info_list */if (sjinfo)
root->join_info_list = lappend(root->join_info_list, sjinfo);
/* * Finally, compute the output joinlist. We fold subproblems together * except at a FULL JOIN or where join_collapse_limit would be * exceeded. */if (j->jointype == JOIN_FULL)
{
/* force the join order exactly at this node */
joinlist = list_make1(list_make2(leftjoinlist, rightjoinlist));
}
elseif (list_length(leftjoinlist) + list_length(rightjoinlist) <=
join_collapse_limit)
{
/* OK to combine subproblems */
joinlist = list_concat(leftjoinlist, rightjoinlist);
}
else
{
/* can't combine, but needn't force join order above here */Node *leftpart,
*rightpart;
/* avoid creating useless 1-element sublists */if (list_length(leftjoinlist) == 1)
leftpart = (Node *) linitial(leftjoinlist);
else
leftpart = (Node *) leftjoinlist;
if (list_length(rightjoinlist) == 1)
rightpart = (Node *) linitial(rightjoinlist);
else
rightpart = (Node *) rightjoinlist;
joinlist = list_make2(leftpart, rightpart);
}
}
else
{
elog(ERROR, "unrecognized node type: %d",
(int) nodeTag(jtnode));
joinlist = NIL; /* keep compiler quiet */
}
return joinlist;
}
/* * make_outerjoininfo * Build a SpecialJoinInfo for the current outer join * * Inputs: * left_rels: the base Relids syntactically on outer side of join * right_rels: the base Relids syntactically on inner side of join * inner_join_rels: base Relids participating in inner joins below this one * jointype: what it says (must always be LEFT, FULL, SEMI, or ANTI) * clause: the outer join's join condition (in implicit-AND format) * * The node should eventually be appended to root->join_info_list, but we * do not do that here. * * Note: we assume that this function is invoked bottom-up, so that * root->join_info_list already contains entries for all outer joins that are * syntactically below this one. */staticSpecialJoinInfo *
make_outerjoininfo(PlannerInfo *root,
Relids left_rels, Relids right_rels,
Relids inner_join_rels,
JoinType jointype, List *clause)
{
SpecialJoinInfo *sjinfo = makeNode(SpecialJoinInfo);
Relids clause_relids;
Relids strict_relids;
Relids min_lefthand;
Relids min_righthand;
ListCell *l;
/* * We should not see RIGHT JOIN here because left/right were switched * earlier */
Assert(jointype != JOIN_INNER);
Assert(jointype != JOIN_RIGHT);
/* * Presently the executor cannot support FOR UPDATE/SHARE marking of rels * appearing on the nullable side of an outer join. (It's somewhat unclear * what that would mean, anyway: what should we mark when a result row is * generated from no element of the nullable relation?) So, complain if * any nullable rel is FOR UPDATE/SHARE. * * You might be wondering why this test isn't made far upstream in the * parser. It's because the parser hasn't got enough info --- consider * FOR UPDATE applied to a view. Only after rewriting and flattening do * we know whether the view contains an outer join. */foreach(l, root->parse->rowMarks)
{
RowMarkClause *rc = (RowMarkClause *) lfirst(l);
if (bms_is_member(rc->rti, right_rels) ||
(jointype == JOIN_FULL && bms_is_member(rc->rti, left_rels)))
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("SELECT FOR UPDATE/SHARE cannot be applied to the nullable side of an outer join")));
}
sjinfo->syn_lefthand = left_rels;
sjinfo->syn_righthand = right_rels;
sjinfo->jointype = jointype;
/* this always starts out false */
sjinfo->delay_upper_joins = false;
sjinfo->join_quals = clause;
/* If it's a full join, no need to be very smart */if (jointype == JOIN_FULL)
{
sjinfo->min_lefthand = bms_copy(left_rels);
sjinfo->min_righthand = bms_copy(right_rels);
sjinfo->lhs_strict = false; /* don't care about this */return sjinfo;
}
/* * Retrieve all relids mentioned within the join clause. */
clause_relids = pull_varnos((Node *) clause);
/* * For which relids is the clause strict, ie, it cannot succeed if the * rel's columns are all NULL? */
strict_relids = find_nonnullable_rels((Node *) clause);
/* Remember whether the clause is strict for any LHS relations */
sjinfo->lhs_strict = bms_overlap(strict_relids, left_rels);
/* * Required LHS always includes the LHS rels mentioned in the clause. We * may have to add more rels based on lower outer joins; see below. */
min_lefthand = bms_intersect(clause_relids, left_rels);
/* * Similarly for required RHS. But here, we must also include any lower * inner joins, to ensure we don't try to commute with any of them. */
min_righthand = bms_int_members(bms_union(clause_relids, inner_join_rels),
right_rels);
foreach(l, root->join_info_list)
{
SpecialJoinInfo *otherinfo = (SpecialJoinInfo *) lfirst(l);
/* ignore full joins --- other mechanisms preserve their ordering */if (otherinfo->jointype == JOIN_FULL)
continue;
/* * For a lower OJ in our LHS, if our join condition uses the lower * join's RHS and is not strict for that rel, we must preserve the * ordering of the two OJs, so add lower OJ's full syntactic relset to * min_lefthand. (We must use its full syntactic relset, not just its * min_lefthand + min_righthand. This is because there might be other * OJs below this one that this one can commute with, but we cannot * commute with them if we don't with this one.) Also, if the current * join is a semijoin or antijoin, we must preserve ordering * regardless of strictness. * * Note: I believe we have to insist on being strict for at least one * rel in the lower OJ's min_righthand, not its whole syn_righthand. */if (bms_overlap(left_rels, otherinfo->syn_righthand))
{
if (bms_overlap(clause_relids, otherinfo->syn_righthand) &&
(jointype == JOIN_SEMI || jointype == JOIN_ANTI ||
!bms_overlap(strict_relids, otherinfo->min_righthand)))
{
min_lefthand = bms_add_members(min_lefthand,
otherinfo->syn_lefthand);
min_lefthand = bms_add_members(min_lefthand,
otherinfo->syn_righthand);
}
}
/* * For a lower OJ in our RHS, if our join condition does not use the * lower join's RHS and the lower OJ's join condition is strict, we * can interchange the ordering of the two OJs; otherwise we must add * lower OJ's full syntactic relset to min_righthand. Here, we must * preserve ordering anyway if either the current join is a semijoin, * or the lower OJ is either a semijoin or an antijoin. * * Here, we have to consider that "our join condition" includes any * clauses that syntactically appeared above the lower OJ and below * ours; those are equivalent to degenerate clauses in our OJ and must * be treated as such. Such clauses obviously can't reference our * LHS, and they must be non-strict for the lower OJ's RHS (else * reduce_outer_joins would have reduced the lower OJ to a plain * join). Hence the other ways in which we handle clauses within our * join condition are not affected by them. The net effect is * therefore sufficiently represented by the delay_upper_joins flag * saved for us by check_outerjoin_delay. */if (bms_overlap(right_rels, otherinfo->syn_righthand))
{
if (bms_overlap(clause_relids, otherinfo->syn_righthand) ||
jointype == JOIN_SEMI ||
otherinfo->jointype == JOIN_SEMI ||
otherinfo->jointype == JOIN_ANTI ||
!otherinfo->lhs_strict || otherinfo->delay_upper_joins)
{
min_righthand = bms_add_members(min_righthand,
otherinfo->syn_lefthand);
min_righthand = bms_add_members(min_righthand,
otherinfo->syn_righthand);
}
}
}
/* * If we found nothing to put in min_lefthand, punt and make it the full * LHS, to avoid having an empty min_lefthand which will confuse later * processing. (We don't try to be smart about such cases, just correct.) * Likewise for min_righthand. */if (bms_is_empty(min_lefthand))
min_lefthand = bms_copy(left_rels);
if (bms_is_empty(min_righthand))
min_righthand = bms_copy(right_rels);
/* Now they'd better be nonempty */
Assert(!bms_is_empty(min_lefthand));
Assert(!bms_is_empty(min_righthand));
/* Shouldn't overlap either */
Assert(!bms_overlap(min_lefthand, min_righthand));
sjinfo->min_lefthand = min_lefthand;
sjinfo->min_righthand = min_righthand;
return sjinfo;
}
/***************************************************************************** * * QUALIFICATIONS * *****************************************************************************//* * distribute_qual_to_rels * Add clause information to either the baserestrictinfo or joininfo list * (depending on whether the clause is a join) of each base relation * mentioned in the clause. A RestrictInfo node is created and added to * the appropriate list for each rel. Alternatively, if the clause uses a * mergejoinable operator and is not delayed by outer-join rules, enter * the left- and right-side expressions into the query's list of * EquivalenceClasses. * * 'clause': the qual clause to be distributed * 'is_deduced': TRUE if the qual came from implied-equality deduction * 'below_outer_join': TRUE if the qual is from a JOIN/ON that is below the * nullable side of a higher-level outer join * 'jointype': type of join the qual is from (JOIN_INNER for a WHERE clause) * 'qualscope': set of baserels the qual's syntactic scope covers * 'ojscope': NULL if not an outer-join qual, else the minimum set of baserels * needed to form this join * 'outerjoin_nonnullable': NULL if not an outer-join qual, else the set of * baserels appearing on the outer (nonnullable) side of the join * (for FULL JOIN this includes both sides of the join, and must in fact * equal qualscope) * * 'qualscope' identifies what level of JOIN the qual came from syntactically. * 'ojscope' is needed if we decide to force the qual up to the outer-join * level, which will be ojscope not necessarily qualscope. * * At the time this is called, root->join_info_list must contain entries for * all and only those special joins that are syntactically below this qual. */staticvoid
distribute_qual_to_rels(PlannerInfo *root, Node *clause,
bool is_deduced,
bool below_outer_join,
JoinType jointype,
Relids qualscope,
Relids ojscope,
Relids outerjoin_nonnullable)
{
Relids relids;
bool is_pushed_down;
bool outerjoin_delayed;
bool pseudoconstant = false;
bool maybe_equivalence;
bool maybe_outer_join;
Relids nullable_relids;
RestrictInfo *restrictinfo;
/* * Retrieve all relids mentioned within the clause. */
relids = pull_varnos(clause);
/* * Cross-check: clause should contain no relids not within its scope. * Otherwise the parser messed up. */if (!bms_is_subset(relids, qualscope))
elog(ERROR, "JOIN qualification cannot refer to other relations");
if (ojscope && !bms_is_subset(relids, ojscope))
elog(ERROR, "JOIN qualification cannot refer to other relations");
/* * If the clause is variable-free, our normal heuristic for pushing it * down to just the mentioned rels doesn't work, because there are none. * * If the clause is an outer-join clause, we must force it to the OJ's * semantic level to preserve semantics. * * Otherwise, when the clause contains volatile functions, we force it to * be evaluated at its original syntactic level. This preserves the * expected semantics. * * When the clause contains no volatile functions either, it is actually a * pseudoconstant clause that will not change value during any one * execution of the plan, and hence can be used as a one-time qual in a * gating Result plan node. We put such a clause into the regular * RestrictInfo lists for the moment, but eventually createplan.c will * pull it out and make a gating Result node immediately above whatever * plan node the pseudoconstant clause is assigned to. It's usually best * to put a gating node as high in the plan tree as possible. If we are * not below an outer join, we can actually push the pseudoconstant qual * all the way to the top of the tree. If we are below an outer join, we * leave the qual at its original syntactic level (we could push it up to * just below the outer join, but that seems more complex than it's * worth). */if (bms_is_empty(relids))
{
if (ojscope)
{
/* clause is attached to outer join, eval it there */
relids = bms_copy(ojscope);
/* mustn't use as gating qual, so don't mark pseudoconstant */
}
else
{
/* eval at original syntactic level */
relids = bms_copy(qualscope);
if (!contain_volatile_functions(clause))
{
/* mark as gating qual */
pseudoconstant = true;
/* tell createplan.c to check for gating quals */
root->hasPseudoConstantQuals = true;
/* if not below outer join, push it to top of tree */if (!below_outer_join)
{
relids =
get_relids_in_jointree((Node *) root->parse->jointree,
false);
qualscope = bms_copy(relids);
}
}
}
}
/*---------- * Check to see if clause application must be delayed by outer-join * considerations. * * A word about is_pushed_down: we mark the qual as "pushed down" if * it is (potentially) applicable at a level different from its original * syntactic level. This flag is used to distinguish OUTER JOIN ON quals * from other quals pushed down to the same joinrel. The rules are: * WHERE quals and INNER JOIN quals: is_pushed_down = true. * Non-degenerate OUTER JOIN quals: is_pushed_down = false. * Degenerate OUTER JOIN quals: is_pushed_down = true. * A "degenerate" OUTER JOIN qual is one that doesn't mention the * non-nullable side, and hence can be pushed down into the nullable side * without changing the join result. It is correct to treat it as a * regular filter condition at the level where it is evaluated. * * Note: it is not immediately obvious that a simple boolean is enough * for this: if for some reason we were to attach a degenerate qual to * its original join level, it would need to be treated as an outer join * qual there. However, this cannot happen, because all the rels the * clause mentions must be in the outer join's min_righthand, therefore * the join it needs must be formed before the outer join; and we always * attach quals to the lowest level where they can be evaluated. But * if we were ever to re-introduce a mechanism for delaying evaluation * of "expensive" quals, this area would need work. *---------- */if (is_deduced)
{
/* * If the qual came from implied-equality deduction, it should not be * outerjoin-delayed, else deducer blew it. But we can't check this * because the join_info_list may now contain OJs above where the qual * belongs. */
Assert(!ojscope);
is_pushed_down = true;
outerjoin_delayed = false;
nullable_relids = NULL;
/* Don't feed it back for more deductions */
maybe_equivalence = false;
maybe_outer_join = false;
}
elseif (bms_overlap(relids, outerjoin_nonnullable))
{
/* * The qual is attached to an outer join and mentions (some of the) * rels on the nonnullable side, so it's not degenerate. * * We can't use such a clause to deduce equivalence (the left and * right sides might be unequal above the join because one of them has * gone to NULL) ... but we might be able to use it for more limited * deductions, if it is mergejoinable. So consider adding it to the * lists of set-aside outer-join clauses. */
is_pushed_down = false;
maybe_equivalence = false;
maybe_outer_join = true;
/* Check to see if must be delayed by lower outer join */
outerjoin_delayed = check_outerjoin_delay(root,
&relids,
&nullable_relids,
false);
/* * Now force the qual to be evaluated exactly at the level of joining * corresponding to the outer join. We cannot let it get pushed down * into the nonnullable side, since then we'd produce no output rows, * rather than the intended single null-extended row, for any * nonnullable-side rows failing the qual. * * (Do this step after calling check_outerjoin_delay, because that * trashes relids.) */
Assert(ojscope);
relids = ojscope;
Assert(!pseudoconstant);
}
else
{
/* * Normal qual clause or degenerate outer-join clause. Either way, we * can mark it as pushed-down. */
is_pushed_down = true;
/* Check to see if must be delayed by lower outer join */
outerjoin_delayed = check_outerjoin_delay(root,
&relids,
&nullable_relids,
true);
if (outerjoin_delayed)
{
/* Should still be a subset of current scope ... */
Assert(bms_is_subset(relids, qualscope));
/* * Because application of the qual will be delayed by outer join, * we mustn't assume its vars are equal everywhere. */
maybe_equivalence = false;
/* * It's possible that this is an IS NULL clause that's redundant * with a lower antijoin; if so we can just discard it. We need * not test in any of the other cases, because this will only be * possible for pushed-down, delayed clauses. */if (check_redundant_nullability_qual(root, clause))
return;
}
else
{
/* * Qual is not delayed by any lower outer-join restriction, so we * can consider feeding it to the equivalence machinery. However, * if it's itself within an outer-join clause, treat it as though * it appeared below that outer join (note that we can only get * here when the clause references only nullable-side rels). */
maybe_equivalence = true;
if (outerjoin_nonnullable != NULL)
below_outer_join = true;
}
/* * Since it doesn't mention the LHS, it's certainly not useful as a * set-aside OJ clause, even if it's in an OJ. */
maybe_outer_join = false;
}
/* * Build the RestrictInfo node itself. */
restrictinfo = make_restrictinfo((Expr *) clause,
is_pushed_down,
outerjoin_delayed,
pseudoconstant,
relids,
nullable_relids);
/* * If it's a join clause (either naturally, or because delayed by * outer-join rules), add vars used in the clause to targetlists of their * relations, so that they will be emitted by the plan nodes that scan * those relations (else they won't be available at the join node!). * * Note: if the clause gets absorbed into an EquivalenceClass then this * may be unnecessary, but for now we have to do it to cover the case * where the EC becomes ec_broken and we end up reinserting the original * clauses into the plan. */if (bms_membership(relids) == BMS_MULTIPLE)
{
List *vars = pull_var_clause(clause, PVC_INCLUDE_PLACEHOLDERS);
add_vars_to_targetlist(root, vars, relids);
list_free(vars);
}
/* * We check "mergejoinability" of every clause, not only join clauses, * because we want to know about equivalences between vars of the same * relation, or between vars and consts. */
check_mergejoinable(restrictinfo);
/* * If it is a true equivalence clause, send it to the EquivalenceClass * machinery. We do *not* attach it directly to any restriction or join * lists. The EC code will propagate it to the appropriate places later. * * If the clause has a mergejoinable operator and is not * outerjoin-delayed, yet isn't an equivalence because it is an outer-join * clause, the EC code may yet be able to do something with it. We add it * to appropriate lists for further consideration later. Specifically: * * If it is a left or right outer-join qualification that relates the two * sides of the outer join (no funny business like leftvar1 = leftvar2 + * rightvar), we add it to root->left_join_clauses or * root->right_join_clauses according to which side the nonnullable * variable appears on. * * If it is a full outer-join qualification, we add it to * root->full_join_clauses. (Ideally we'd discard cases that aren't * leftvar = rightvar, as we do for left/right joins, but this routine * doesn't have the info needed to do that; and the current usage of the * full_join_clauses list doesn't require that, so it's not currently * worth complicating this routine's API to make it possible.) * * If none of the above hold, pass it off to * distribute_restrictinfo_to_rels(). */if (restrictinfo->mergeopfamilies)
{
if (maybe_equivalence)
{
if (process_equivalence(root, restrictinfo, below_outer_join))
return;
/* EC rejected it, so pass to distribute_restrictinfo_to_rels */
}
elseif (maybe_outer_join && restrictinfo->can_join)
{
if (bms_is_subset(restrictinfo->left_relids,
outerjoin_nonnullable) &&
!bms_overlap(restrictinfo->right_relids,
outerjoin_nonnullable))
{
/* we have outervar = innervar */
root->left_join_clauses = lappend(root->left_join_clauses,
restrictinfo);
return;
}
if (bms_is_subset(restrictinfo->right_relids,
outerjoin_nonnullable) &&
!bms_overlap(restrictinfo->left_relids,
outerjoin_nonnullable))
{
/* we have innervar = outervar */
root->right_join_clauses = lappend(root->right_join_clauses,
restrictinfo);
return;
}
if (jointype == JOIN_FULL)
{
/* FULL JOIN (above tests cannot match in this case) */
root->full_join_clauses = lappend(root->full_join_clauses,
restrictinfo);
return;
}
}
}
/* No EC special case applies, so push it into the clause lists */
distribute_restrictinfo_to_rels(root, restrictinfo);
}
/* * check_outerjoin_delay * Detect whether a qual referencing the given relids must be delayed * in application due to the presence of a lower outer join, and/or * may force extra delay of higher-level outer joins. * * If the qual must be delayed, add relids to *relids_p to reflect the lowest * safe level for evaluating the qual, and return TRUE. Any extra delay for * higher-level joins is reflected by setting delay_upper_joins to TRUE in * SpecialJoinInfo structs. We also compute nullable_relids, the set of * referenced relids that are nullable by lower outer joins (note that this * can be nonempty even for a non-delayed qual). * * For an is_pushed_down qual, we can evaluate the qual as soon as (1) we have * all the rels it mentions, and (2) we are at or above any outer joins that * can null any of these rels and are below the syntactic location of the * given qual. We must enforce (2) because pushing down such a clause below * the OJ might cause the OJ to emit null-extended rows that should not have * been formed, or that should have been rejected by the clause. (This is * only an issue for non-strict quals, since if we can prove a qual mentioning * only nullable rels is strict, we'd have reduced the outer join to an inner * join in reduce_outer_joins().) * * To enforce (2), scan the join_info_list and merge the required-relid sets of * any such OJs into the clause's own reference list. At the time we are * called, the join_info_list contains only outer joins below this qual. We * have to repeat the scan until no new relids get added; this ensures that * the qual is suitably delayed regardless of the order in which OJs get * executed. As an example, if we have one OJ with LHS=A, RHS=B, and one with * LHS=B, RHS=C, it is implied that these can be done in either order; if the * B/C join is done first then the join to A can null C, so a qual actually * mentioning only C cannot be applied below the join to A. * * For a non-pushed-down qual, this isn't going to determine where we place the * qual, but we need to determine outerjoin_delayed and nullable_relids anyway * for use later in the planning process. * * Lastly, a pushed-down qual that references the nullable side of any current * join_info_list member and has to be evaluated above that OJ (because its * required relids overlap the LHS too) causes that OJ's delay_upper_joins * flag to be set TRUE. This will prevent any higher-level OJs from * being interchanged with that OJ, which would result in not having any * correct place to evaluate the qual. (The case we care about here is a * sub-select WHERE clause within the RHS of some outer join. The WHERE * clause must effectively be treated as a degenerate clause of that outer * join's condition. Rather than trying to match such clauses with joins * directly, we set delay_upper_joins here, and when the upper outer join * is processed by make_outerjoininfo, it will refrain from allowing the * two OJs to commute.) */staticbool
check_outerjoin_delay(PlannerInfo *root,
Relids *relids_p, /* in/out parameter */Relids *nullable_relids_p, /* output parameter */bool is_pushed_down)
{
Relids relids;
Relids nullable_relids;
bool outerjoin_delayed;
bool found_some;
/* fast path if no special joins */if (root->join_info_list == NIL)
{
*nullable_relids_p = NULL;
returnfalse;
}
/* must copy relids because we need the original value at the end */
relids = bms_copy(*relids_p);
nullable_relids = NULL;
outerjoin_delayed = false;
do
{
ListCell *l;
found_some = false;
foreach(l, root->join_info_list)
{
SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(l);
/* do we reference any nullable rels of this OJ? */if (bms_overlap(relids, sjinfo->min_righthand) ||
(sjinfo->jointype == JOIN_FULL &&
bms_overlap(relids, sjinfo->min_lefthand)))
{
/* yes; have we included all its rels in relids? */if (!bms_is_subset(sjinfo->min_lefthand, relids) ||
!bms_is_subset(sjinfo->min_righthand, relids))
{
/* no, so add them in */
relids = bms_add_members(relids, sjinfo->min_lefthand);
relids = bms_add_members(relids, sjinfo->min_righthand);
outerjoin_delayed = true;
/* we'll need another iteration */
found_some = true;
}
/* track all the nullable rels of relevant OJs */
nullable_relids = bms_add_members(nullable_relids,
sjinfo->min_righthand);
if (sjinfo->jointype == JOIN_FULL)
nullable_relids = bms_add_members(nullable_relids,
sjinfo->min_lefthand);
/* set delay_upper_joins if needed */if (is_pushed_down && sjinfo->jointype != JOIN_FULL &&
bms_overlap(relids, sjinfo->min_lefthand))
sjinfo->delay_upper_joins = true;
}
}
} while (found_some);
/* identify just the actually-referenced nullable rels */
nullable_relids = bms_int_members(nullable_relids, *relids_p);
/* replace *relids_p, and return nullable_relids */
bms_free(*relids_p);
*relids_p = relids;
*nullable_relids_p = nullable_relids;
return outerjoin_delayed;
}
/* * check_redundant_nullability_qual * Check to see if the qual is an IS NULL qual that is redundant with * a lower JOIN_ANTI join. * * We want to suppress redundant IS NULL quals, not so much to save cycles * as to avoid generating bogus selectivity estimates for them. So if * redundancy is detected here, distribute_qual_to_rels() just throws away * the qual. */staticbool
check_redundant_nullability_qual(PlannerInfo *root, Node *clause)
{
Var *forced_null_var;
Index forced_null_rel;
ListCell *lc;
/* Check for IS NULL, and identify the Var forced to NULL */
forced_null_var = find_forced_null_var(clause);
if (forced_null_var == NULL)
returnfalse;
forced_null_rel = forced_null_var->varno;
/* * If the Var comes from the nullable side of a lower antijoin, the IS * NULL condition is necessarily true. */foreach(lc, root->join_info_list)
{
SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(lc);
if (sjinfo->jointype == JOIN_ANTI &&
bms_is_member(forced_null_rel, sjinfo->syn_righthand))
returntrue;
}
returnfalse;
}
/* * distribute_restrictinfo_to_rels * Push a completed RestrictInfo into the proper restriction or join * clause list(s). * * This is the last step of distribute_qual_to_rels() for ordinary qual * clauses. Clauses that are interesting for equivalence-class processing * are diverted to the EC machinery, but may ultimately get fed back here. */void
distribute_restrictinfo_to_rels(PlannerInfo *root,
RestrictInfo *restrictinfo)
{
Relids relids = restrictinfo->required_relids;
RelOptInfo *rel;
switch (bms_membership(relids))
{
case BMS_SINGLETON:
/* * There is only one relation participating in the clause, so it * is a restriction clause for that relation. */
rel = find_base_rel(root, bms_singleton_member(relids));
/* Add clause to rel's restriction list */
rel->baserestrictinfo = lappend(rel->baserestrictinfo,
restrictinfo);
break;
case BMS_MULTIPLE:
/* * The clause is a join clause, since there is more than one rel * in its relid set. *//* * Check for hashjoinable operators. (We don't bother setting the * hashjoin info if we're not going to need it.) */if (enable_hashjoin)
check_hashjoinable(restrictinfo);
/* * Add clause to the join lists of all the relevant relations. */
add_join_clause_to_rels(root, restrictinfo, relids);
break;
default:
/* * clause references no rels, and therefore we have no place to * attach it. Shouldn't get here if callers are working properly. */
elog(ERROR, "cannot cope with variable-free clause");
break;
}
}
/* * process_implied_equality * Create a restrictinfo item that says "item1 op item2", and push it * into the appropriate lists. (In practice opno is always a btree * equality operator.) * * "qualscope" is the nominal syntactic level to impute to the restrictinfo. * This must contain at least all the rels used in the expressions, but it * is used only to set the qual application level when both exprs are * variable-free. Otherwise the qual is applied at the lowest join level * that provides all its variables. * * "both_const" indicates whether both items are known pseudo-constant; * in this case it is worth applying eval_const_expressions() in case we * can produce constant TRUE or constant FALSE. (Otherwise it's not, * because the expressions went through eval_const_expressions already.) * * This is currently used only when an EquivalenceClass is found to * contain pseudoconstants. See path/pathkeys.c for more details. */void
process_implied_equality(PlannerInfo *root,
Oid opno,
Expr *item1,
Expr *item2,
Relids qualscope,
bool below_outer_join,
bool both_const)
{
Expr *clause;
/* * Build the new clause. Copy to ensure it shares no substructure with * original (this is necessary in case there are subselects in there...) */
clause = make_opclause(opno,
BOOLOID, /* opresulttype */false, /* opretset */
(Expr *) copyObject(item1),
(Expr *) copyObject(item2));
/* If both constant, try to reduce to a boolean constant. */if (both_const)
{
clause = (Expr *) eval_const_expressions(root, (Node *) clause);
/* If we produced const TRUE, just drop the clause */if (clause && IsA(clause, Const))
{
Const *cclause = (Const *) clause;
Assert(cclause->consttype == BOOLOID);
if (!cclause->constisnull && DatumGetBool(cclause->constvalue))
return;
}
}
/* Make a copy of qualscope to avoid problems if source EC changes */
qualscope = bms_copy(qualscope);
/* * Push the new clause into all the appropriate restrictinfo lists. */
distribute_qual_to_rels(root, (Node *) clause,
true, below_outer_join, JOIN_INNER,
qualscope, NULL, NULL);
}
/* * build_implied_join_equality --- build a RestrictInfo for a derived equality * * This overlaps the functionality of process_implied_equality(), but we * must return the RestrictInfo, not push it into the joininfo tree. */RestrictInfo *
build_implied_join_equality(Oid opno,
Expr *item1,
Expr *item2,
Relids qualscope)
{
RestrictInfo *restrictinfo;
Expr *clause;
/* * Build the new clause. Copy to ensure it shares no substructure with * original (this is necessary in case there are subselects in there...) */
clause = make_opclause(opno,
BOOLOID, /* opresulttype */false, /* opretset */
(Expr *) copyObject(item1),
(Expr *) copyObject(item2));
/* Make a copy of qualscope to avoid problems if source EC changes */
qualscope = bms_copy(qualscope);
/* * Build the RestrictInfo node itself. */
restrictinfo = make_restrictinfo(clause,
true, /* is_pushed_down */false, /* outerjoin_delayed */false, /* pseudoconstant */
qualscope, /* required_relids */
NULL); /* nullable_relids *//* Set mergejoinability info always, and hashjoinability if enabled */
check_mergejoinable(restrictinfo);
if (enable_hashjoin)
check_hashjoinable(restrictinfo);
return restrictinfo;
}
/***************************************************************************** * * CHECKS FOR MERGEJOINABLE AND HASHJOINABLE CLAUSES * *****************************************************************************//* * check_mergejoinable * If the restrictinfo's clause is mergejoinable, set the mergejoin * info fields in the restrictinfo. * * Currently, we support mergejoin for binary opclauses where * the operator is a mergejoinable operator. The arguments can be * anything --- as long as there are no volatile functions in them. */staticvoid
check_mergejoinable(RestrictInfo *restrictinfo)
{
Expr *clause = restrictinfo->clause;
Oid opno;
if (restrictinfo->pseudoconstant)
return;
if (!is_opclause(clause))
return;
if (list_length(((OpExpr *) clause)->args) != 2)
return;
opno = ((OpExpr *) clause)->opno;
if (op_mergejoinable(opno) &&
!contain_volatile_functions((Node *) clause))
restrictinfo->mergeopfamilies = get_mergejoin_opfamilies(opno);
/* * Note: op_mergejoinable is just a hint; if we fail to find the operator * in any btree opfamilies, mergeopfamilies remains NIL and so the clause * is not treated as mergejoinable. */
}
/* * check_hashjoinable * If the restrictinfo's clause is hashjoinable, set the hashjoin * info fields in the restrictinfo. * * Currently, we support hashjoin for binary opclauses where * the operator is a hashjoinable operator. The arguments can be * anything --- as long as there are no volatile functions in them. */staticvoid
check_hashjoinable(RestrictInfo *restrictinfo)
{
Expr *clause = restrictinfo->clause;
Oid opno;
if (restrictinfo->pseudoconstant)
return;
if (!is_opclause(clause))
return;
if (list_length(((OpExpr *) clause)->args) != 2)
return;
opno = ((OpExpr *) clause)->opno;
if (op_hashjoinable(opno) &&
!contain_volatile_functions((Node *) clause))
restrictinfo->hashjoinoperator = opno;
}